It is customary to incorporate, e.g., fragrance oils, in many liquid products, including products intended for use as household cleaning, disinfecting, sanitizing, bleaching, deodorizing or drain opening products. One method used to accomplish this end is to disperse the material having said lubricating tendency (hereinafter illustratively referred to as fragrance oils) in the liquid product, typically a primarily aqueous product, with the aid of a surface active agent, after which the product is filled into bottles that are then capped. However, such a procedure has several disadvantages. First, the dispersion step entails the use of expensive surfactants that add to the cost of the product. Moreover, this dispersion process attenuates the desired characteristics of the fragrance oil, thereby requiring the use of additional fragrance oils to achieve like results.
Efforts to reduce the costs of these products by adding the fragrance oils and the bulk of the liquid product to the bottle separately introduced new problems in the bottling operation. Thus, the fragrance oils often splashed onto the threads of the bottle neck and served as an unwanted lubricant between the threads on the neck of the bottle and the threads of the cap, during the capping operation.
The capping step is generally an automatic operation which employs a torque sensing device to signal the end of the operation in which the cap is screwed on to the bottle. As the cap is being screwed onto the top of the bottle by the capper, the torque being applied to the cap increases. When a preset torque level is reached the torque sensor signals the capper to cease applying a torque to the cap. Where fragrance oils are present on the bottle neck threads there is less friction between the bottle neck threads and screw cap threads during the capping operation. As a consequence, the cap is screwed further into the bottle neck threads before the torque being applied by the capper reaches its preset limit that signals the termination of the screwing process. The end result is a higher immediate release torque on the capped bottle, that is to say that a greater force is required to unscrew the cap from the bottle than is the case when there are no fragrance oils on the bottle neck threads. Because only a small and indefinite number of bottle necks become wetted with the fragrance oils it is not possible to make allowance for the effect noted and it is inherently impossible to obtain uniform release torques.
A better idea of the problem may perhaps be gleaned by a comparison of the Immediate Release Torque data obtained from capped bottles that were bottled in accordance with "normal" bottling operation (i.e. where no fragrance oil was added to the bottle before capping) and that obtained from capped bottles bottled by a process which also includes the separate or discrete addition of fragrance oils in liquid form to the bottle. This data is summarized in the table below:
______________________________________ Immediate Release Torque (in.-lbs.) Fragrance Oil "Normal" Operation Added in Liquid Form ______________________________________ X = 20 in.-lb. X = 30 in.-lb. S = 1.7 S = 5.0 .+-. 3S = 15-25 in.-lb. .+-. 3S = 15-45 in.-lb. ______________________________________ where X = Average torque necessary to unscrew capped bottled. S = Standard deviation of sample. .+-. 3S = Range of 99.7% of the data points.
As this data indicates the standard derivation, i.e. the degree to which the individual torque measurements differ from each other, is 2.94 times greater when the fragrance oils are added in liquid form during the bottling operation compared to the case in which fragrance oils are not added. This is a clear indication of the difficulty in obtaining a uniform release torque rate with the former bottling operation.